Three judges at a freedom of information tribunal had previously ruled in favour of Rob Evans, of the Guardian, who had challenged a decision by the Information Commissioner to uphold a refusal by the Government departments to release the correspondence.

But in a written statement the Attorney General today said:

I consider that such correspondence enables the Prince of Wales better to understand the business of government; strengthens his relations with ministers; and enables him to make points which he would have a right - and indeed a duty - to make as monarch.

If such correspondence is to take place at all, it must be under conditions of confidentiality. Without such confidentiality, both the Prince of Wales and ministers will feel seriously inhibited from exchanging views candidly and frankly, and this would damage the Prince of Wales' preparation for kingship.

A Guardian News and Media spokeswoman said they intended to take the case further and challenge the veto in the High Court.